The present invention relates to control systems and pertains particularly to control systems for simultaneously applying brakes to a vehicle in response to a shift in the direction of the vehicle.
Heavy-duty earth-working vehicles are frequently operated in a manner to require frequent shifting between forward and reverse directions. This frequent reversal of directions is required in order to most efficiently and effectively utilize the machine. This reversal of direction frequently occurs at a very high speed in order to obtain the most efficient use of the machine. One problem with such high-speed reversal of direction is that the energy of the vehicle must be somehow dissipated before the vehicle is put into the reverse direction.
Numerous approaches to this problem have been proposed in the past. However, such prior art approaches to this problem have drawbacks.
The prior art approaches to this problem are exemplified in the following U.S. Pats. No. 3,348,644 issued Oct. 24, 1967 to Hilpert; No. 3,437,184 issued Apr. 8, 1969 to Wilson; No. 3,540,556 issued Nov. 17, 1970 to Snoy et al; No. 3,540,559 issued Nov. 17,. 1970 to Shore; and No. 3,604,544 issued Sept. 14, 1971 to Floyd C. Ross.
Among the drawbacks of these prior art systems is that they apply the vehicle brakes regardless of the speed of the vehicle. The problem with this approach is that it actuates the brakes of the vehicle at such slow speed that it unnecessarily interferes with the operation of the vehicle. That is, the brakes are cycled during the shift between the forward and reverse, or vice versa, regardless of the speed.
At very low speeds the transmission and clutch system of a vehicle can absorb the momentum of the vehicle without undue stress thereof and thus save the time required for the brake systems to sequence. Thus, a considerable savings in time and operation of control systems is achieved.